German Patent No. 44 21 881 (DE 44 21 881 A1) discusses a fuel injector having a valve needle with a filter element mounted thereon or inside of it. The filter element is used to keep any particles and impurities, upstream from the sealing seat in the interior of the fuel injector, away from the sealing seat, thereby avoiding clogging and/or leakages at the sealing seat. The filter element is designed in the form of a screening sock which envelops the valve needle at least partially.
The fuel injector discussed in DE 44 21 881 A1 is such that the production and installation of a sock-shaped filter element may be complex and, thus, cost-intensive. Because of the large surface of the filter element, it is susceptible to twisting and shifting during the operation of the fuel injector, due to considerable valve-needle movement.